1. Field of the Invention
The present invention relates to a cyclopentaphenanthrene-based compound and an organoelectroluminescent device employing the same. More particularly, the present invention relates to a cyclopentaphenanthrene-based compound and an organoelectroluminescent device including an organic layer formed of the cyclopentaphenanthrene-based compound.
2. Description of the Related Art
Organoelectroluminescent devices are active emission display devices that emit light by recombination of electrons and holes in a thin layer (hereinafter, referred to as “organic layer”) formed of a fluorescent or phosphorescent organic compound when a current is supplied to the organic layer. The organoelectroluminescent devices have advantages such as lightness, simple constitutional elements, an easy fabrication process, superior image quality, and a wide viewing angle. In addition, the organoelectroluminescent devices can perfectly create dynamic images, achieve high color purity, and have electrical properties suitable for portable electronic equipment due to low power consumption and low driving voltage.
Eastman Kodak Co. has developed an organoelectroluminescent device with a multi-layered structure including an aluminum quinolinol complex layer and a triphenylamine derivative layer (U.S. Pat. No. 4,885,211), and an organoelectroluminescent device including an organic light-emitting layer formed of a low molecular weight material capable of emitting light in a broad wavelength range from UV to infrared light (U.S. Pat. No. 5,151,629).
Light-emitting devices are self-emitting devices and have advantages such as a wide viewing angle, good contrast, and a rapid response time. Light-emitting devices can be classified into inorganic light-emitting devices using an emitting layer formed of an inorganic compound and organic light-emitting devices (OLEDs) using an emitting layer formed of an organic compound. OLEDs show better brightness, driving voltage, and response speed characteristics and can create polychromatic light, compared to inorganic light-emitting devices, and thus, extensive research into OLEDs has been conducted.
Generally, OLEDs have a stacked structure including an anode, an organic light-emitting layer, and a cathode. OLEDs may also have various structures such as anode/hole injection layer/hole transport layer/emitting layer/electron transport layer/electron injection layer/cathode or anode/hole injection layer/hole transport layer/emitting layer/hole blocking layer/electron transport layer/electron injection layer/cathode.
Materials used for OLEDs can be classified into vacuum-depositable materials and solution-coatable materials according to an organic layer formation process. Vacuum-depositable materials must have a vapor pressure of 10−6 torr or more at 500° C. or less, and may be low molecular weight materials having a molecular weight of 1,200 or less. Solution-coatable materials must have solubility sufficient to form solutions, and include mainly an aromatic or heterocyclic ring.
When manufacturing organoelectroluminescent devices using a vacuum deposition process, manufacturing costs may increase due to use of a vacuum system, and it may be difficult to manufacture high-resolution pixels for natural color displays using a shadow mask. On the other hand, when manufacturing organoelectroluminescent devices using a solution coating process, e.g., inkjet printing, screen printing, or spin coating, the manufacturing process is simple, manufacturing costs are low, and a relatively high resolution can be achieved compared to when using a shadow mask.
However, when using solution-coatable materials, the performance (e.g., thermal stability, color purity) of light-emitting molecules is lowered compared to when using vacuum-depositable materials. Even though the light-emitting molecules of the solution-coatable materials have good performance, there arise problems that the materials, when formed into an organic layer, are gradually crystallized to grow into a size corresponding to a visible light wavelength range, and thus, the grown crystals scatter visible light, thereby causing a turbidity phenomenon, and pinholes, etc. may be formed in the organic layer, thereby causing device degradation.
Japanese Patent Laid-Open Publication No. 1999-003782 discloses a two naphthyl-substituted anthracene compound that can be used in an emitting layer or a hole injection layer. However, the anthracene compound is poorly soluble in a solvent, and further, an organoelectroluminescent device using the anthracene compound has unsatisfactory characteristics.
Therefore, it still needs to develop organoelectroluminescent devices which have good thermal stability and are improved in driving voltage, brightness, efficiency, and color purity characteristics.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.